Adhesion to an un-scored surface of these PVC enclosures is sometimes a challenge. Do you plan the wall facade to be removable or permanent?
I use these adhered with super glue to the walls for tie downs with the self stick garbage they come with peeled off first. If you want permanent walls you could zip tie the egg crate to those then spray foam on to the egg crate as a medium to get good attachment.
If you do not want permanent walls then you could always cut acrylic or even pvc to size, score it first and create the walls that way then loose mount them to the T12